Komplexkatalyse: XXV. 31P-NMR-spektroskopische charakterisierung der anti- und syn-struktur von C3-substituierten η3-allylbis(triarylphosphit)-nickel(II)-hexafluorophosphat-komplexen und der mechanismus der durch [C3H5Ni(P(OPh)3)2]PF6 katalysierten 1,4-trans-polymerisation des butadiens

The reaction of the η₃-allylbis(triarylphosphite)nickel(II) complexes with butadiene under chain propagation to give the polybutadienyl complex, 3-RC₃H₄Ni(P(OAr)₃)₂]PF₆, was monitored by ³¹P NMR spectroscopy. In the case of the triphenylphosphite complex both the anti- and the syn-configuration could be identified by means of their different AB spectra. The anti-syn isomerization, the higher reactivity of the thermodynamically more stable syn-form, and the formation of the anti-structure as a result of each individual butadiene insertion step was also proved. From these observations an experimentally well-grounded mechanism of the trans regulation with the anti-syn isomerization as the rate-determining step could be derived for the first time.